中文摘要：

于2013年1月—2014年12月,应用Granier热扩散探针对中国西南西双版纳地区13年生（幼龄期）、25年生（中龄期）、33年生（中老龄期）、50年生（老龄期）4个林龄橡胶树的液流密度进行了连续2年的观测,分析了橡胶树液流密度的变化特征,并推算了林分蒸腾量。结果表明：在日、月、季节和年尺度上,25年生橡胶树的平均液流密度均显著大于13、33和50年生（P〈0.01）;从年尺度上看,50年生橡胶林的蒸腾量显著大于33和13年生（P〈0.01）;西双版纳不同林龄橡胶树的液流密度大致呈抛物线变化,峰值出现在生命活动最旺盛的中龄期（25年生）;橡胶林的蒸腾量总体上随林龄的增大而增加,最大值出现在老龄期（50年生）;西双版纳地区橡胶林的年平均液流密度为16.42±3.24 g·m^（-2）·s^（-1）,年平均蒸腾量为870.58±145.89 mm。

英文摘要：

Sap flow density of rubber trees（ Hevea brasiliensis） of four ages（ 13 years old,young; 25 years old,middle-aged; 33 years old,middle-old-aged; and 50 years old,over-mature） in Xishuangbanna of Southwest China was measured by the Granier thermal diffusion probe technique from January 2013 to December 2014,and then scaled up to estimate stand-level transpiration. The results showed that,on day,month,season and year time-scales,the middle-aged trees had the highest mean sap flow density,being significantly higher than the other aged trees（ P0.01）. The over-mature stands had the highest annual transpiration rate（ 1212.49±42.80 mm per year）,being significantly higher than those of the young and middle aged stands（ P0.01）. With the increase of stand age,the sap flow density of rubber trees generally followed a parabola change,with the peak in the most vigorous middle-aged stand. The transpiration of rubber stands increased with increasing stand age in general,and the over-mature stand had the highest transpiration. The mean annual sap flow density of rubber stands in Xishuangbanna was estimated as 16.42±3.24 g·m^（-2）·s^（-1） and the mean annual transpiration as 870.58±145.89 mm.